In a large bowl, whisk together the flour, baking powder, baking soda, sugar, and salt.

Add the chilled, cubed butter and cut it into the flour mixture until the butter pieces are about pea-sized.

Stir in the chopped kimchi until evenly distributed.

Pour in the buttermilk and mix just until a dough forms. Do not overmix.

Turn the dough onto a lightly floured surface and pat or roll it into a 1-inch-thick rectangle.

Cut the dough into thirds and stack the layers on top of each other. Gently press the dough back into a 1-inch-thick rectangle. Repeat this folding and stacking process one more time to create flaky layers.

If the dough becomes soft or warm at any point, place it in the refrigerator for 10–15 minutes before continuing.

Pat the dough into a 1-inch-thick rectangle and cut into 3-inch squares.

Place the biscuits on a parchment paper lined baking sheet and freeze for 20–30 minutes.

While the biscuits chill, preheat the oven to 425°F (220°C).

Brush the tops of the biscuits with egg wash.

Bake for 20–22 minutes, or until the biscuits are tall and golden brown.

Serve warm and enjoy.